Burner for pulverized fuel



Patented Nov. 15, 1938 BURNER FOR PULVERIZED FUEL L. V. Andrews,Worcester, Mass, assignor to Riley Stoker Corporation,

Worcester, Mass., a corporation of Massachusetts Application February27, 1936, Serial No. 66,075 4 Claims. (01. 116-104) This inventionrelates to burners for pulverized fuel, andmore particularly to burnersof the type having a nozzle arranged to discharge a stream of pulverizedfuel and primary air, and means for delivering secondary'air around theoutside of the fuel stream.

It has been proposed heretofore to mount a fuel spreader comprising aseries of substantially radial vanes at the discharge end of the fuelnozzle to whirl the fuel and deflect it outwardly into the secondary airstream. While burners so constructed operate with high efficiency undernormal conditions, it is in some cases difficult to obtain a wide rangeof fuel burning rates and particularly to maintain ignition whenoperating at low capacities. Furthermore the prior fuel spreaders havebeen somewhat difficult and expensive to manufacture. It is accordinglyone object of the present invention to provide a pulverized fuel burnerwhich can be operated efficiently over a wide range of capacity.

It is a further object of the present invention to provide a pulverizedfuel burner so constructed and arranged as to ensure proper ignition ofthe fuel even at low capacities.

It is a further object of the invention to provide a pulverized fuelburner which will be comparatively simple and inexpensive tomanufacture.

With these and other objects in view, as will be apparent to thoseskilled in the art, the invention resides in the combination of partsset forth in the specification and covered by the claims appendedhereto.

Referring to the drawing'illustrating one embodiment of the invention,and in which like reference numerals indicate like parts,

Fig. 1 is a somewhat diagrammatic longitudinal section through apulverized fuel burner;

Fig. 2 is an end view of the fuel nozzle and the fuel spreader mountedtherein;

Fig. 3 is a section on the line 3-3 of Fig. 2; and

Fig. 4 is a side elevation of the fuel spreader mounted in the nozzle,the latter being shown in longitudinal section.

In the drawing I have shown a vertical furnace wall II! of refractorymaterial provided with a burner opening II. A horizontal cylindricalpipe or nozzle I2 is mounted in front of the opening I I, the front endof this nozzle being supported in a hollow receiving head I4 having aninlet passage I5. Pulverized fuel and primary air are delivered to thepassage I 5 from a suitable source, and the stream is discharged fromthe nozzle I2 rearwardly through the opening II. A casing I6 surroundsthe nozzle I2, and secondary air under pressure is delivered to thiscasing from a suitable source and escapes therefrom through the openingII in surrounding relation to the fuel stream. The admission of air maybe controlled by dampers I1.

In order to ensure thorough and rapid mixing of the fuel with thesecondary air and thus obtain a short and turbulent flame, a fuelspreader I9 is mounted at the I2, this spreader being arranged to whirlthe fuel and throw it outwardly into the surrounding secondary airstream. In the embodiment illustrated the spreader I9 comprises a seriesof defleeting vanes and 2| mounted in substantially radial positions andeach arranged at an angle to the general direction of the stream flow.These vanes are comparatively thin and of uniform width throughout theirlengths, and they can be readily cut from commercially available stripsof flat steel without bending. The outer ends of the vanes are arrangedin a circle having a diameter slightly less than the inside of thenozzle I2, and they are held in assembled relationship by means of a,ring 23 concentric with the nozzle and welded to the front edges of thevanes intermediate their lengths. This ring can be formed by a steel rodof circular cross-section bent into the desired shape.

It will be noted that the vanes 2I are somewhat longer than the vanes20. Furthermore the longer vanes 2| are few in number as compared withthe shorter vanes. The inner ends of the shorter vanes 20 are arrangedin a circle, and the longer vanes 2I extend beyond the shorter vanes andinto this circle. With this construction, the resistance to flow at thecentral part of the spreader is greatly reduced as compared with priorconstructions, and yet the desired whirl is imparted to the entire fuelstream.

Provision is preferably made for adjusting the fuel spreader I 9longitudinally of the nozzle I2. For this purpose the inner ends of thelonger vanes 2| are welded to a cylindrical sleeve or hub 24, and thissleeve is fastened by means of a set screw 25 to the rear end of a tube21 coaxial with the nozzle I2. This tube 21 is slidably supported in thehead I4, and a handle 28 is secured to the front end of the tube tofacilitate its longitudinal adjustment.

The operation of the invention will now be apparent from the abovedisclosure. The stream of pulverized fuel and primary air flows throughthe receiving head I 4 and the nozzle I2 and is discharged rearwardlythrough the opening- I I.

to the casing I 6-" discharge end of the nozzle Secondary air isdelivered from the casing IE to the opening II in surrounding relationto the fuel stream. The vanes 20 and 2| whirl the fuel and throw itoutwardly into the secondary air, ensuring a short and turbulent flame.The annular space between the sleeve 24 and the inner ends of theshorter vanes 20 is comparatively unobstructed, so that considerablefuel will flow therethrough even when the burner is operating at lowcapacities. This provides a central core for the flame which iscomparatively rich in fuel and as a result ignition can be readilymaintained, this being facilitated by the action of the inner portionsof the longer vanes 21 which tend to concentrate the fuel in localizedstreams.

The improved fuel spreader is comparatively,

stantially radial positions with the inner ends of some of the vanessecured to the hub, the inner ends of the other vanes being'spacedoutwardly from the hub to provide a plurality of openings through whicha substantial flow of fuel may take place during the burner operation.

2. A pulverized fuel burner comprising a nozzle arranged to discharge astream of pulverized fuel and air, a series of deflecting vanes mountedin substantially radial positions in the path of the fuel at thedischarge end of the nozzle and shaped to whirl the fuel, some of thevanes being longer than the others, and a central hub secured to theinner ends of the longer vanes, the inner ends of the shorter vanesbeing spaced outwardly from the hub to provide a plurality of openingsthrough which a substantial flow of fuel may take place during theburner operation.

3. A pulverized fuel burner comprising a cylindrical nozzle arranged todischarge a stream of pulverized fuel and air, a series of deflectingvanes mounted in substantially radial positions in the path of the fuelat the discharge and of the nozzle and shaped to whirl the fuel, theouter ends of the vanes being arranged in a circle and some of the vanesbeing longer than the others, and a central hub secured to the innerends of the longer vanes, the inner ends of the shorter vanes beingspaced outwardly from the hub to provide a plurality of openings throughwhich a substantial flow of fuel may take place during the burneroperation.

4. A'pulverized fuel burner comprising a cylindrical nozzle arranged todischarge a stream of pulverized fuel and air, a series of deflectingvanes mounted in substantially radial positions in the path of the fuelat the discharge end of the nozzle and shaped to whirl the fuel, theouter ends of the vanes being arranged in a circle and some of the vanesbeing longer than the others, a ring secured to the vanes intermediatetheir lengths, a central hub secured tothe inner ends of the longervanes, and a support for said hub, the inner ends of the shorter vanesbeing spaced outwardly from the hub to provide a plurality of openingsthrough which a substantial flow of fuel may take place during theburner operation.

L. V. ANDREWS.

